Narrow Results

With an increased emphasis on time-domain and multi-messenger astrophysics, astrophysical transients have catapulted in importance over the past few years. Astronomers are discovering an increasingly diverse set of transient phenomena. Oftentimes, the menagerie of transients are analyzed using simplified models designed for a single transient. Using such inappropriate models often leads to incorrect interpretations of these models. This misuse often lies in a poor understanding of the basic physics powering astrophysical transients. In this paper, we review this basic physics, building up the different physical components behind transient emission toward increasingly complex models behind astrophysical phenomena. These discussions allow us to better understand the misconceptions in our current interpretations of astrophysical transients.

It has been hypothesized recently that core collapse supernovae are triggered by mildly relativistic jets following observations of radio properties of these explosions. Association of a jet, similar to a gamma-ray burst jet but only slower, allows shock acceleration of particles to high energy and non-thermal neutrino emission from a supernova. Detection of these high energy neutrinos in upcoming kilometer scale Cherenkov detectors may be the only direct way to probe inside these astrophysical phenomena as electromagnetic radiation is thermal and contains little information. Calculation of high energy neutrino signal from a simple and slow jet model buried inside the pre-supernova star is reviewed here. The detection prospect of these neutrinos in water or ice detector is also discussed in this brief review. Jetted core collapse supernovae in nearby galaxies may provide the strongest high energy neutrino signal from point sources.

I describe and critically evaluate a variety of methods, from simple parametrizations to non-parametric methods, to model the background expansion history in the presence of dark energy. Motivated by these approaches, I review the prospects of determining the properties of dark energy with future experiments, in particular the Dark Energy Survey (DES) and SuperNova/Acceleration Probe (SNAP). Finally, I outline the importance of being able to constrain whole classes of dark energy models, and present recent work that comprehensively studied the observational signature of general scalar field models.

Neutrinos play the critical roles in nucleosyntheses of light-to-heavy mass elements in core-collapse supernovae (SNe). The light element synthesis is affected strongly by neutrino oscillations (MSW effect) through the ν-process in outer layers of supernova explosions. Specifically the ⁷Li and ¹¹B yields increase by factors of 1.9 and 1.3 respectively in the case of large mixing angle solution, normal mass hierarchy, and sin² 2θ₁₃ = 2 × 10⁻³ compared to those without the oscillations. In the case of inverted mass hierarchy or nonadiabatic 13-mixing resonance, the increment of their yields is much smaller. We thus propose that precise constraint on mass hierarchy and sin² 2θ₁₃ is given by future observations of Li/B ratio or Li abundance in stars and presolar grains which are made from supernova ejecta. Gamma ray burst (GRB) nucleosynthesis in contrast is not affected strongly by thermal neutrinos from the central core which culminates in black hole (BH), although the effect of neutrinos from proto-neutron star prior to black hole formation is still unknown. We calculate GRB nucleosynthesis by turning off the thermal neutrinos and find that the abundance pattern is totally different from ordinary SN nucleosynthesis which satisfies the universality to the solar abundance pattern.

I first give an update on our study of the energy asymmetry given the proto-neutron star during the time when the neutrino sphere is near the surface of the proto-neutron star, at a time 10-20s, using the modified URCA process. With the magnetic field strong enough for a large fraction of the electrons produced with the anti-neutrinos to be in the lowest Landau level, we predict a pulsar velocity of 1.03 × 10⁻⁴(T/10¹⁰K)⁷km/s, which reaches 1000 km/s if T ≃ 9.96 × 10¹⁰K. Also, using the recent results of the MiniBoone study, with two sterile neutrinos, I give results for pulsar kicks during the first 10s.

We clarify important physics issues related to the recently established new mass limit for magnetized white dwarfs which is significantly super-Chandrasekhar. The issues include, justification of high magnetic field and the corresponding formation of stable white dwarfs, contribution of the magnetic field to the total density and pressure, flux freezing, variation of magnetic field and related currents therein. We also attempt to address the observational connection of such highly magnetized white dwarfs.

Recently, an anisotropic cosmological model was proposed. An arbitrary one-form, which picks out a privileged axis in the universe, was added to the Friedmann–Robertson–Walker (FRW) line element. The distance-redshift relation was modified such that it is direction-dependent. In this paper, we use the Union2 dataset and 59 high-redshift gamma-ray bursts (GRBs) to give constraints on the anisotropy of the universe. The results show that the magnitude of anisotropy is about D = -0.044±0.018, and the privileged axis points toward the direction (l₀, b₀) = (306.1°±18.7°, -18.2°±11.2°) in the galactic coordinate system. The anisotropy is small and the isotropic cosmological model is an excellent approximation.

The influence of strong electron screening (SES) on electron capture (EC) plays a key role in supernovae explosions. We investigate the influence of SES on EC of iron group nuclei by the linear response theory model (LRTM) and the plasma sphere theory model (PSTM). The corrections of the Q-value, the electron chemical potential, electron energy, the Coulomb wave correction factor, and nuclear blinding energy by SES are considered. The screening rates even decrease by $\sim 81.89\%$ and $\sim 78.32\%$ by PSTM and LRTM, respectively. We compare our screening results with those of Fuller et al. (FFN), Aufderheide et al. (AUFD), Nabi et al. (NKK), and Martinez-Pinedo et al. (MLD). Our screening rates can be lowered about by $1\sim 2$, 2, and 1 orders of magnitude than those of AUFD (FFN), NKK, and MLD, respectively.

In this paper, we mainly focus on 22 old white dwarfs and present two new magnetic monopoles (MMs) energy cooling resources models (I) and (II) based on MMs catalytic nuclear decay. We discussed their luminosity, and compared with the observations. The luminosities for these old White Dwarf stars (WDs) for models (I) and (II) are well in agreement with the observations $L_{\mathrm{\text{rad}}}$ and the differences are no more than one order magnitude at relativistic low temperature (e.g. $T_6=0.01$). However, at relativistic high temperature (e.g. $T_6=10$), the observations $L_{\mathrm{\text{rad}}}$ can be four and two orders of magnitude lower than those of models (I) and (II), respectively. We also compared the results of models (I) and (II) by scaling factor $k_3$. One can see that the maximum of the luminosities for model (I) are 185.2705 and 512.7054 times larger than those of model (II) for old WD $1247+551^a$ at $T_6=0.01$, 10, respectively. On the other hand, the minimum of the luminosities for model (I) are 7.3563 and 34.8064 times larger than those of model (II) for old WD 1444-175 at $T_6=0.01$, 10, respectively. By considering the effect on the mass radius relationship by the number of the MMs captured in WDs and catalytic nuclear decay, our results show that the study of model (II) may be an improving estimation, and the monopole-catalyzed nucleon decay process could be preventing white dwarfs from cooling down into a stellar graveyard by keeping them hot.

I discuss the state of the art in the search for stellar collapse neutrinos and the perspectives of this field. The implications for neutrino physics of a high statistics supernova neutrino burst detection by the network of operating experiments are also reviewed.

Dark Energy is the dominant constituent of the universe and we have little understanding of it. We describe a new project aimed at measuring the dark energy equation of state parameter, w, to a statistical precision of ~5% with four separate techniques. The survey will image 5000 deg² in the southern sky and collect 300 million galaxies, 30,000 galaxy clusters, and 2000 Type Ia supernovae. The survey will be carried out using a new 3 deg² mosaic camera mounted at the prime focus of the 4m Blanco telescope at CTIO.

The origin of cosmic rays (CR) is supposed to be closely connected with supernovae (SNe) which create the conditions favorable for various mechanisms of the CR acceleration to operate effectively. First, modern ideas about the physics of the SN explosion are briefly discussed: the explosive thermonuclear burning in degenerate white dwarfs resulting in Type Ia SNe and the gravitational collapse of stellar cores giving rise to other types of SNe (Ib, Ic, IIL, IIP). Next, we survey some global properties of the SNe of different types: the total explosion energy distribution of various components (kinetic energy of the hydrodynamic flow, electromagnetic radiation, temporal behavior of the neutrino emission and individual energies of different neutrino flavors). Then, we discuss in the possibility of direct hydrodynamic acceleration by the shock wave breakout and the properties of the SN shocks in the circumstellar medium. Then the properties of the neutrino radiation from the core-collapse SNe and a possibility to incorporate both the LSD Mont Blanc neutrino event and that recorded by the K II and IMB detectors into a single scenario are described in detail. Finally, the issues of the neutrino nucleosynthesis and of the connection between supernova and gamma-ray bursts are discussed.

A massive neutrino has nonzero magnetic moment and is involved in the electromagnetic interactions with external fields and photons. The electromagnetic neutrino moving in matter can emit the spin light $(SL\nu )$ in the process of transition between two quantum states in matter. In quite resembling way an electron can emit spin light in moving background composed of neutrinos, that is “the spin light of an electron in neutrino flux” $(SL{e}_{\nu })$. In this paper we obtain the exact solution for the wave function and energy spectrum for an electron moving in a neutrino flux and consider the $SL{e}_{\nu }$ as the transition process between two electron quantum states in the background. The $SL{e}_{\nu }$ radiation rate, power and emitted photon energy are calculated. Notably, the energy spectrum of the emitted $SL{e}_{\nu }$ photons can span up to gamma-rays. We argue that the considered $SL{e}_{\nu }$ can be of interest for astrophysical applications, for supernovae processes in particular.

The collapse of massive stars have been used to explain many of the largest outbursts known to mankind, from supernovae to hypernovae to gamma-ray bursts. These explosions differ in their level of asymmetry and the spectral energy of the photons they emit. It is likely that such a wide range in the nature of these explosions requires more than one explosion mechanism to extract the gravitational potential energy released during the collapse. Three major classes of mechanisms have been proposed: neutrino-driven, magnetic-field driven, collapsar (black hole accretion disk) driven. This review discusses each mechanism in turn, discussing the current state-of-the-art calculations along with their observational predictions. We conclude with a summary of the current observational constraints on these models.

The detection of neutrinos from SN 1987A opened a new era in neutrino astrophysics in the last century. We present a historical view about registration of the neutrino signal from supernova SN 1987A in the Large Magellanic Cloud by the BAKSAN liquid scintillator detector and by the two water Cherenkov detectors — Kamiokande-II and IMB. All three detectors observed a total neutrino signal of 24 events at 7:35 UT 23 February, 1987. I will concentrate mostly about the BAKSAN supernova group analysis of the neutrino signal, which was already done in the years 1987 and 1988. The results of this analysis (determination of average properties of the neutrino signal: the total energy of neutrino emission, the effective neutrino temperature, the total luminosity of the neutrino signal, duration of the neutrino burst) are presented. The common analysis of all three detectors shows that these 'parameters' have good agreement with the general theoretical description of explosions of supernovae. The analysis shows that the inclusion of the BAKSAN data is very important for the understanding of the SN87A event. The latest results of 20 years of observation of our Galaxy by the BAKSAN scintillation telescope show that the upper limit of the mean frequency of gravitational collapses is <0.13 yr^-1 at a 90% confidence level.

We consider a cosmological model with a variable gravitational constant, G, based on a scalar–tensor theory. Using the recent observational data for the Hubble diagram of type Ia supernovae (SNeIa), we find a phenomenological expression describing the variation of G. The corresponding variation of the fine structure constant α within multidimensional theories is also computed and is shown not to support known constraints on Δα/α.

Recent measurements are suggesting that we live in a flat Universe and that its present accelerating stage is driven by a dark energy component whose equation of state may evolve in time. Assuming two different parametrizations for the function ω(z), we constrain their free parameters from a joint analysis involving measurements from X-ray luminosity of galaxy clusters and SNe type Ia data.

We discuss results of 2D simulations of magnetorotational (MR) mechanism of core collapse supernova explosions. Due to the nonuniform collapse, the collapsed core rotates differentially. In the presence of an initial poloidal magnetic field its toroidal component appears and grows with time. Increased magnetic pressure leads to the formation of a compression wave which moves outwards. It transforms into the fast MHD shock wave (supernova shock wave). The shape of the MR supernova explosion qualitatively depends on the configuration of the initial magnetic field. For a dipole-like initial magnetic field, the supernova explosion develops mainly along the rotational axis, forming a mildly collimated jet. A quadrupole-like initial magnetic field leads to the explosion developing mainly along the equatorial plane. The magnetorotational instability was found in our simulations. The supernova explosion energy grows with an increase of the initial core mass and rotational energy of the core, and corresponds to the observational data.

Cosmic ray acceleration may occur at a supernova shock expanding into a circumstellar wind. Self-similar solutions for the cosmic ray distribution are derived firstly when diffusion is isotropic and secondly when the wind sustains a magnetic field in the form of a Parker spiral.

We outline an improved cosmology which uses a higher-dimensional space of the type implied by unification, where the cosmological "constant" decays from an unbounded value at the big bang to an acceptable value today. This model leads to a better understanding of inflation and is in good agreement with observations of galaxies.